Sketchup 3d model import with wrong topology?
Those are the result of triangulating faces, possibly because of the file format used for the exporting (e.g. .3ds will do that regardless whether you asked it to or not). 

To get quads-based topology back:


It should be possible to convert them back to quads with Alt+J, but this might not work in all cases (depends on topology complexity). You will need to convert faces which were converted not in desired way manually;
use another file format for import / export, e.g. .fbx or .dae.


Note: the need in converting depends on the final result you're aiming to.